Can a Variable Resistor Control Current in a Welding Circuit?

[Ricka]

I wonder if I can get some opinions on this circuit before I go looking for the parts. It seems simple enough even I can build it. Alternatively, does anyone have any dope on making a saturale core reactor (magnetic amplifier) to control an AC welder? All I can find on the web is theory. As a further alternative, I've seen reference to putting a resistor in the ground lead to reduce current; would it be feasible to use a variable resistor for current control? Thank you.

http://i287.photobucket.com/albums/ll127/Mary1218_photos/SAVE-1-1.jpg

Rick A

 

[skeptic2]

You don't say how much current your welder draws nor the current rating of the SCRs or lamp dimmer. You must remember that the current rating of semiconductors drops the warmer they get. This means their current rating must be much higher than you think you'll need and they should be well heat sinked.

For high currents I strongly favor the magnetic amplifier approach. Here is a link to one reference for making a magnetic amplifier.

http://sparkbangbuzz.com/mag-amp/mag-amp.htm

 

[Ricka]

Skeptic2: Thank you for your interest. The SCR's in the diagram are rated at 90a and I don't exceed about 60a (I only need this current control for TIG welding on thin stuff) and on a low duty cycle, so I would't think I'd overheat them. But assuming I stay within the design limits of the circuit, does it look workable to you?

I'd found that link before, and, while it demonstrates the principle, doesn't tell me much about scaling it up to the amperage I need. A lot of welders used to use mag amps and I'd happily use one if I could find it, but, like everything else, they've moved on to solid state circuitry.

Rick A